1. Field of the Invention
The present invention relates to towing accessories and, more particularly without limitation, to tow bars for connecting a towing vehicle to a vehicle to be towed.
2. Description of the Related Art
A tow bar is generally used for connecting a towing vehicle to a vehicle to be towed, the latter sometimes being referred to herein as a towed vehicle. For applications wherein the towed vehicle will be towed at a speed sufficient to move with the flow of traffic on a public roadway, the tow bar, which connects the front end of the towed vehicle to the rear end of the towing vehicle, generally has two tow bar legs with the front ends of the tow bar legs forming the apex of an isosceles triangle and the rear ends of the tow bar legs being spaced apart to form the sides of the triangle. The triangular configuration causes the towed vehicle to closely track the towing vehicle along straightaways and around corners.
For tow bar applications, such as where heavy, massive equipment will be moved a relatively short distance, such as where an airliner is to be backed away from a terminal for example, the tow bar generally has only one tow bar leg. For such applications, one end of the tow bar leg may be connected to the front end of the vehicle to be moved and the other end of the tow bar leg being connected to the front end of the towing vehicle so the operator of the towing vehicle can face the towed vehicle and can carefully observe the response of the towed vehicle as it is being slowly moved by the towing vehicle.
Most tow bars must be designed to accommodate variations in attitude that inherently exist between towing and towed vehicles, which variations are constantly and continuously changing. One such variation in attitude between the vehicles is the instantaneous sidewise tilt of the towing vehicle relative to the instantaneous sidewise tilt of the towed vehicle, such as the rocking motion which occurs when traversing uneven or rough pavement for example. This phenomenon, sometimes referred to as “roll”, can be accommodated by tow bar apparatus designed to accommodate rotations between the towing and towed vehicles about a fore-to-aft horizontal axis, see the “x”-axis in FIG. 1.
Another such variation in attitude between the vehicles is the instantaneous horizontal direction in which the towing vehicle is traveling relative to the instantaneous horizontal direction in which the towed vehicle is traveling, such as when the towed vehicle is being pulled around an unbanked corner for example. This phenomenon, sometimes referred to as “yaw”, can be accommodated by apparatus designed to accommodate rotations between the towing and towed vehicles about a vertical axis, see the “y”-axis in FIG. 1.
Finally, another such variation in attitude between the vehicles is the instantaneous elevation of the towing vehicle relative to the instantaneous elevation of the towed vehicle. A related variation in attitude between the vehicles is the instantaneous ascent/descent orientation of the towing vehicle relative to the instantaneous ascent/descent orientation of the towed vehicle. Both of these related variations in attitude can be accommodated by apparatus designed to accommodate rotations between the towing and towed vehicles about a transverse, horizontal axis, sometimes referred to as the “pitch” axis, see the “z”-axis in FIG. 1.
During actual towing operations, all combinations of roll, yaw and pitch are continuously occurring and changing. Prior art is replete with tow bar designs that have been developed in an attempt to accommodate these phenomena, some of those designs being more successful than others. For example, a hitch ball/hitch ball-receiver combination securing a tow bar to a towing vehicle can theoretically accommodate all three of the roll, yaw and pitch phenomena. Although the ability of such a combination to accommodate yaw is encouraging, unfortunately the ability of such a combination to accommodate either roll or pitch is extremely limited where failure to closely abide by such limitations can produce disastrous and even fatal results.
A commonly used arrangement involves using a conventional receiver hitch in combination with a square hitch shank. Although such an arrangement may be convenient for connecting a tow bar to a towing vehicle, this type of connection by itself provides absolutely no ability to accommodate any one of the three roll, yaw or pitch phenomena. As a result, the tow bar itself and/or the connections between the tow bar and the towed vehicle must be relied upon to provide a solution for minimizing the potentially dangerous aspects arising from these three phenomena.
Typically, a tow bar is first connected to a towing vehicle followed by connecting the tow bar to the towed vehicle. It is difficult, if not impossible, to perfectly align a towing vehicle with, and perfectly space the towing vehicle from, the towed vehicle so the tow bar legs can be easily and conveniently connected to the towed vehicle. Many towing hitch arrangements of towed vehicles require precise fore-to-aft, horizontal, and/or angular alignment of tow bar leg connectors with mating connectors of a towed hitch arrangement so pivot pins can be inserted through orifices of those mating connectors while the mating parts of the tow bar are physically held in place relative to those of the towed vehicle. Such activity can be extremely stressful, sometimes requiring the efforts of more than one person. Therefore, an ability to manually apply roll, yaw and pitch rotations could be very useful while connecting a tow bar to a hitching arrangement of a towed vehicle.
Such stress and effort could be further reduced if a tow bar could be constructed of light-weight, high-strength material. Such materials have been developed but most are either too expensive for use in tow bar construction, or are frangible and cannot reliably endure the adverse environment to which tow bars are normally subjected, particularly when the frangible material must be penetrated in order to assemble the various components of a tow bar. Such penetrations would severely degrade the structural integrity of many apparatii, particularly tow bars, constructed from such material.
What is needed is a tow bar constructed of light-weight, high-strength materials which one person working alone can easily lift and use to connect a towing vehicle to a towed vehicle.
What is also needed is a tow bar constructed of light-weight, high-strength materials, including frangible material, which one person working alone can easily lift and use to connect a towing vehicle to a towed vehicle.
What is further needed is a tow bar constructed of light-weight, high-strength materials, including frangible material, which can be assembled without penetrating the frangible material.
What is still further needed is a locking member for a tow bar constructed of light-weight, high-strength materials, including frangible material, wherein the locking member does not require penetration of the frangible material.